0utput is data that has been processed
into a useful form called information. That is, a computer
processed input into
output. Computers generate several types of output, depending on the hardware
and software being used and the requirements of the user. You may choose to
display or view this output on a monitor, print it on a printer, or listen to it
through speakers or a headset.

Four
common types of output are:

I.Text

II.Graphics

III.Audio

IV.Video

1)

Text

Consists of characters that are
used to create words, sentences, and paragraphs. A character is a letter, number, punctuation mark, or any other
symbol that requires one byte of computer storage space.

2)

Graphics

Are digital representations of
non-text information such as drawings, charts, and photographs? Graphics
also can be animated, giving them the illusion of motion.

3)

Audio

Is music, speech, or any other
sound? Recall that sound waves, such as the human voice or music, are
analog. To store such sounds, a computer converts the sounds from a
continuous analog signal into a digital format. Most output devices
require that the computer convert the digital format back into analog
signals.

OUTPUT

Output is data that has been processed
into a useful form called information. That is a computer processes input into
output. Computers generate several types of output, depending on the hardware
and software being used and the requirement of the user. You may choose to
display or view this output on a monitor, print it on a printer or listen to it
though speakers or a headset. Four common types of output are text, graphics,
audio and video.

Text consists of characters that are used to create word, sentences and
paragraphs. A character is a letter, number, punctuation mark or any other
symbol that requires one byte of computer storage space.

Graphics are digital representations of
context information such as drawings, charts and photographs. Graphics also
can be animated, giving them the illusion of motion. Displaying a series of
still images in rapid sequence creates animation.

Audio in music, speech or any other sound. Recall that sound waves, such
as the human voice or music, are analog. To store such sound, a computer
converts the sounds from a continuous analog signal into a digital format.
Most output devices require that the computer convert the digital format back
into analog signal. Video consists of images that are played back at speeds
that provide the appearance of full motion. Video often is captured with a
video input devices such as a camera or VCR.A video capture card converts an
analog video signal into a digital that a computer can understand. The digital
signal then is stored on the computer’s hard disk.

WHAT ARE OUTPUT DEVICES?

An output device is any computer component capable of conveying
information to a user. Commonly used output devices include display devices,
speakers, headset, data projector, facsimile machines and multifunction
devices.

DATA PROJECTORS

A data projector takes the image that displays on a
computer screen and projector it into a screen so that an audience of people
can see the image clearly. Data projectors can be large devices attached to
ceiling or wall in an auditorium, or they can be small portable devices. Two
types of smaller, lower-cost units are LCD projector s and DLP projectors.

An LCD
projector, which uses liquid crystal display technology, attaches directly to
a computer and uses its own light source to display the information shown on
the computer screen. Because LCD projectors tend to produce lower-quality
images, some users prefer to use a DLP projector for shaper, brighter images.

A digital
light processing (DLP) projectors uses tiny mirrors to reflect light,
producing crisp, bright, colorful images that remain in focus and can be seen
clearly even in a well-lit room.

LIQUID CRYSTAL
DISPLAY

The most common application of liquid crystal
technology is in liquid crystal displays (LCDs). From the ubiquitous
wristwatch and pocket calculator to an advanced VGA computer screen, this type
of display has evolved into an important and versatile interface.

A liquid crystal display consists of an array of tiny
segments (called pixels) that can be manipulated to present information. This
basic idea is common to all displays, ranging from simple calculators to a
full color LCD television.

Why are liquid crystal displays important? The first
factor is size. As will be shown in the following sections, an LCD consists
primarily of two glass plates with some liquid crystal material between them.
There is no bulky picture tube. This makes LCDs practical for applications
where size (as well as weight) is important.

In general, LCDs use much less power than their
cathode-ray tube (CRT) counterparts. Many LCDs are reflective, meaning that
they use only ambient light to illuminate the display. Even displays that do
require an external light source (i.e. computer displays) consume much less
power than CRT devices.

Liquid crystal displays do have drawbacks, and these
are the subjects of intense research. Problems with viewing angle, contrast
ratio, and response time still need to be solved before the LCD replaces the
cathode-ray tube. However with the rate of technological innovation, this day
may not be too far into the future.

We will restrict this discussion to traditional
nomadic LCDs since the major technological advances have been developed for
this group of devices. Other LC applications, such as those employing polymer
stabilization of LC structure, are discussed in the appropriate section
covering those materials.

CRT MONITORS

A CRT monitor, or monitor is a
display device that consists of a screen housed in a plastic or metal case. A color
monitor display text, graphics and video information in color. Color
monitor are used widely with all types of computers because most of today’s
software is designed to display information in color.

Monitor that display only one color are considered
monochrome. A monochrome monitor display text, graphics and video information
in one color (usually white, amber or green) on a black background. Because
monochrome monitors are less expensive than color monitors, some organizations
use them for applications that do not require color or detailed graphics, such
as order entry. To enhance the quality of their
graphics display, some monochrome monitors use gray scaling, which involves
using many shades of gray from white to black to form the images.

Like a television set, the core of
a CRT monitor is a large glass tube called a cathode ray tube (CRT). The
screen, which is the front of the tube, is coated with tiny dot of phosphor
material that glows when electrically charged. Inside the CRT, an electron
beam moves back and forth across the back of the screen, causing the to glow,
which produces an images on the screen.

Each dot, called a pixel (short for picture element),
is a single point an electronic image. Monitors consist of hundreds, thousands
or millions of pixels arranged in rows and columns that can be used to create
images. The pixels are so close together that they appear connected.

CRT monitors are used with a
variety of computers. The CRT monitors used with desktop computers are
available in a number of sizes, with the more common being 15, 17, 19 and 21
inches. The size of a monitor is measured diagonally from corner to corner.

Most monitors are referred to by
their viewable size, which is the diagonal measurement of the cathode ray tube
inside the monitor and is larger than the actual viewing area provided by the
monitor.

MONITOR

The computer monitor, screen or VDU
(visual Display Unit) is the most common output devices.

ADVANTAGES

DISADVANTAGES

Relatively cheap
and reliable, can displaytext and graphics
in a wide range of colors. They are also quiet and do not
waste paper.

No permanent copy
to keep and unsuitable for users with visual problems.

Screen sizes are measured
diagonally and are still quoted in inches. Popular size are 15 inches (38 cm)
and 17 inches ( 43 cm ). Larger monitor make working at a computer easier on
the eyes and are essential for use in DTP (Desktop Publishing) and CAD
work.

Most computers are similar in many
ways to a television. They use cathode ray tubes

(CRTS) containing an electron gun
at the back the tubes which fires electrons at groups of phosphor dots
coating the inside of the screen. On a color monitor each group of phosphor
dots is made up of green, blue, and red dot makes up a pixel of visible
light. By varying the intensity of each of these primary colors, the
whole pixel will appear to the human eye as any colored desired.

The quality of a monitor’s
display depends largely on its resolution, dot pitch and refresh rate. The
resolution, or sharpness and clarity, of a monitor is related directly to the
number of pixel it can display. Resolution is expressed as two of pixels:

1)The number of columns of pixel

2)The numbers of pixel a monitor can display

A monitor with a higher resolution display a greater
number of pixels, a higher resolution causes images to display smaller on the
screen. The ideal monitor resolution to use is a matter of preference. A
higher resolution is desirable for graphic application; a lower resolution
usually is satisfactory for application such as word processing.

GAS
PLASMA MONITORS.

For even larger displays, some large business or power
users prefer gas plasma monitors, which can measure more than 42 inches and
hang directly on a wall. Gas plasma monitors use gas plasma technology, which
substitutes a layer of gas the liquid crystal material in an LCD monitor. When
voltage is applied, the gas glows and produces the pixels that form an image.
Gas plasma monitors offer larger screen sizes and higher display quality than
LCD monitors but are much more expensive.

MONITOR QUALITY

The quality of a monitor’s display depends largely
on its:

Resolution.

The resolution or sharpness and clarity,
of a monitor are related directly to the number of pixels it can display.
Resolution is expressed as two separate numbers: the number of columns of
pixels and the number of rows of pixels a monitor can display.

Dot pitch.

Pitch is a measure of image
clarity. The dot pitch is the vertical distance between each pixel on a
monitor. The smaller the distance between the pixels, the sharper the
displayed image.

Refresh
rate.

A
monitor’s refresh rate should be fast enough to maintain a constant,
flicker-free image. A slower refresh rate causes the image to fade and then
flicker as it is redrawn, which can headaches for user. Refresh rate is
measured according to hertz, which
is the number of times per second the screen is redrawn.

HIGH-DEFINITION
TELEVISION

High-definition television (HDTV) is a type of television set that works
with digital broadcasting signals and support a wider screen and higher
resolution display than a standard television set. When you use a standard
television set as a monitor for your computer, the output must be converted
to an analog signal that can be displayed by the television set.

With HDTV, the broadcast signals are digitized when they are sent.
Digital television signals provide two advantages over analog signals.
First, digital signals produce a higher-quality picture. Second, many
programs can be broadcast on a single digital channel, whereas only one
program can be broadcast on an analog channel. Because HDTV is capable of
receiving text, graphics, audio and video, you can use HDTV as a monitor
while browsing the Internet. When the cost of HDTV becomes more reasonable,
home user will begin to use it as their computer’s display device.

PRINTERS

Printers
are primary output devices used to generate information from the computers.
Reports, sales receipts letters and memos are all examples of output by the
computer through the printer. These output are often referred to as “Hard
Copies” or “Printout” in computer jargon.

Printers are very similar to
electric typewriters minus the keys. With speed taken into consideration,
printers can be classified into character line, or page printers.

Character printers are the slowest
printers since they print character by character. There are two types of
character printers:

Dot-Matrix
printers

Letter-Quality
printers

Character is
printed line-by-line, hence increasing printing speed that uses
electromechanical parts. Page printers are high speed, non-impact printers
with printing rates so high that output appears to be printed a page at a
time. Electrostatics printers form character on chemically treated paper by
using charge pins.

Laser beam
printers use a combination of laser beam and electrographic techniques to
create printed output at tremendous speed.

TYPES OF
PRINTERS

DOT-MATRIX PRINTERS

ŘLimited to situations where carbon copies
are needed and the quality is not too important.

ŘTypical uses might be in warehouse where
duplicate copies of orders need to produce quickly and cheaply.

ŘThe printing quality is low because of
this impact these printers can be quite noise.

ŘThe purchase cost is low and the running
costs are very low.

ŘCan print fairly quickly, if you remember
that multiple copies are being printed in one print run.

ŘRobust and can operate in harsh
environments.

ŘIf several sheets of self-carbonating
paper are placed into the printer then the impact will produce multiple
copies.

INK-JET PRINT

A
popular choice for home and school use where small amounts of printing are
done

The
ink cartridges can be expensive so running costs can be high.

Speed
is slow compared to a laser printer.

Relatively
inexpensive and produce high quality black and white or color

LASER PRINTERS

Color laser printers are ‘considerably more expensive’
(but their speed and

high
quality output means they are becoming more popular).

Quiet and fast and produce high quality printouts.

Running cost are low because although toner cartridges are
expensive to

replace,
they last a long time.

SPEAKER

In any sound system, ultimate quality
depends on the speakers. The best recording, encoded on the most advanced
storage device and played by a top-of-the-line deck and amplifier, will sound
awful if the system is hooked up to poor speakers. A system's speaker is the
component that takes the electronic signal stored on things like CDS, Tapes,
and DVDs and turns it back into actual sound that we can hear.

In this article, we'll find out exactly how
speakers do this. We'll also look at how speaker designs differ, and see how
these differences affect sound quality. Speakers are amazing pieces of
technology that have had a profound impact on our culture. But at their heart,
they are remarkably simple devices.

PLOTTER

A device that draws pictures on paper based on commands from computer.
Plotter differs from printer in that they draw lines using a pen. As a result,
they can produce continuous lines, whereas printer can only simulate lines by
printing a closely spaced series of dot. Multicolor plotter use different
colored pens to draw different colors.

In general, plotters are considerably more expensive than printer. They
are used in engineering application where precision is mandatory.

Graphics plotter – the flat- bed
plotter uses high precision motors to draw on paper with colored ink pen. The
motors move an arm across the paper in the‘x’direction and a pen unit up and down the arm in the ‘y’
direction. An electromagnet lifts and drops the pen onto the paper.

Plotters are often used in science
and engineering application for drawing building plans, printer circuit boards
and machine parts. They are fast and accurate but relatively expensive compared
to printer. They can produce far larger printouts than standard printer, up to
the size of a small room.

FACSIMILE
(FAX) MACHINE

A facsimile (fax) machine is a device that transmits and
receives documents overtelephone lines. The documents can contain text, drawings, or
photographs, or can behandwritten. When sent or received via a fax machine, these
documents are known asfaxes. A stand-alone fax machine scans the original documents,
converts the imageinto digitized data, and transmits the digitized image (Figure
5-34). A fax machine at thereceiving end reads the incoming data, converts the digitized
data into an image, andprints or stores a copy of the original image.

Fax
capability also can be added to your computer using a fax modem. A fax modem isa
communications device that allows you to send (and sometimes receive) electronicdocuments
as faxes (Figure 5 –35). A fax modem transmits computer-prepared

documents
that have been digitized with a scanner or digital camera. A fax modem islike
a regular modem except that is designed to transmit documents to a fax machine or
to another fax modem.

When a computer (instead of a fax machine) receives a fax, you can view
thedocument
on the screen or print it using special fax software. The quality of the viewedor
printed fax is less than that of a word processing document because the fax

actually
is a large image. If you have optical character recognition (OCR) software,you
also can edit the document. A fax modem can be an external peripheral thatplugs
into a port on the back of the system unit or an internal card that is inserted
intoan
expansion slot on the motherboard. In addition, most fax modems function asregular
modems.